You know what question I get asked most as a racecar driver? No, not, "Do you get scared?" and, amazingly, not even, "How fast does your car go?" The most commonly asked question is, "Why do you have to be fit to drive a racecar? All you do is sit down and turn a wheel?"

My response is usually simple: "Grow a brain." But sometimes I like to indulge in the physics behind why a driver must be an elite athlete to handle a racecar.

Now, I shall indulge once more.

Firstly, the comment about how you have no issue in your Porsche when you weigh as much as an African bush elephant on steroids is not really relevant. In fact, even if you race machines like GT sports cars, or even junior open-wheel racecars, you don't need to be particularly fit. At least not yet, anyway.

Every racecar driver will tell you how fit they are, even if they race slower cars on less physically demanding tracks. So, to be fair, if you ask the question, "Do you need to be fit?" to one of these drivers, you are perhaps not as much of an idiot as you might think.

The driver will, of course, lie and explain how he runs a 4:30 mile. But when you look up their times from the annual 5k Thanksgiving dash, it will show they were beaten by a one-legged man dressed as a turkey.

Elite fitness only becomes a necessity in very high-performance machines, but that doesn't include NASCAR. Why? Well, on road courses, NASCAR stock cars are slow, as they have zero grip to utilize their monster engines. Simply put, it's not what they were designed to do, and g-forces are therefore minimal. Ovals are not physical either. Sure, the g-forces are higher (albeit far lower than in an open-wheel car), but you can rest your head against a pad, and not much else is going on — no gear changes, no tight bends with vicious braking zones followed by heavy acceleration, and the steering effort is much lower, too. It really is not that tough.

And that's why Tony Stewart is fat. Because he doesn't need to be fit.

On the flip side, an IndyCar driver needs to be an elite athlete, because the cars have a mountain of grip and they drive on physically demanding tracks. Road courses are tough, but street circuits are hell. They are exceptionally bumpy, and a car as fast as an IndyCar provides little time for the driver to rest. G-forces are especially high and the steering weighs about as much as an overindulgent NFL linebacker.

Imagine shoulder-pressing a 40 lb. weight while strapped to a bucking bronco. The longer the corner, the longer you must hold the weight above your head, despite being frantically banged around. Then add g-forces akin to what a fighter pilot may feel, and you get an idea of what it's like to drive a high-downforce racecar.

Your heart rate could run close to 90 percent of its maximum, and your race is two-hours long. You will be drained, out of breath, and your arms will feel like they belong to SpongeBob Squarepants.

On an oval in an IndyCar, you still have to deal with the insanely high steering weight. G-forces (despite being over 5g in places) are actually not a problem, as they remain constant and a molded seat and head pad holds you up. It's the abrupt changes that get you, and ovals are smooth and consistent so, like with NASCAR, cardio is not an issue. Your arms may fall off, though.

If you race a stock Porsche 911, or a Star Mazda open-wheel car, you don't have to be much fitter than your average guy or gal who remains active. A few days a week of moderate exercise should work fine. What is important, however, is to build up a base level of fitness greater than required, so you are prepared should the opportunity arise to move up into a more powerful, physically demanding car.

In most cases, drivers don't need to be excessively fit. But those driving high-horsepower, high-downforce machines such as prototype Le Mans, IndyCar or Formula One cars, must be incredibly fit to handle immense g-forces, high steering loads and tight, bumpy racetracks.

To back this up, here's a story I have never before told publicly:

Back in 2007, just a week before I won the Indy Lights championship (the step below IndyCar), I was offered a test with the Target Chip Ganassi IndyCar team. It was August in Florida and the temperature was 94 degrees Fahrenheit, with high humidity.

I hadn't trained a great deal during my time in Indy Lights, as the fitness required was nothing crazy or extreme. I only drove the IndyCar that day for an hour, broken up into short runs of maybe five minutes each. Half-way through my session I could barely talk. I asked to get out, faking needing a piss so I could catch a quick breather.

My face became blotchy with purple splodges, and I felt incredibly sick. I could hardly breath, and my arms didn't work. I wasn't sure I could get back in the car, meaning I would have to admit to my lack of fitness, and potentially blow my opportunity to impress a team as esteemed as Ganassi. Like Eminem said, you only get one shot.

After a glass of water, I held back the vomit and clambered back into the car. Fortunately, I finished my session without crashing and ran to the bathroom to finally throw up.

That is how physical a racecar can be. No one on the race team knew of my troubles and I kept it a deathly secret to avoid embarrassment (until now – DAMMIT!). After that, I trained for hours and hours a day — swimming, biking and running. I became fit enough to place well in an IRONMAN 70.3 triathlon — consisting of a 1.2-mile swim, 56-mile bike, followed by a half-marathon. That is the level of fitness it requires to race an IndyCar and not throw up.

Next time your buddy laughs about how racecar drivers don't need to be fit, tell him he's an idiot. Unless he's talking about Tony Stewart. Then you can laugh out loud.

About the author: @Alex_Lloyd began racing in the U.S. in 2006. He won the Indy Lights championship in 2007. He's competed in the Daytona 24-hour twice and the Indianapolis 500 four times — placing fourth in 2010. The native of MADchester, UK began racing karts at age 8, open-wheel race cars at 16 and finished second to Formula One World Champion - and close friend - Lewis Hamilton, in the 2003 British Formula Renault Championship, followed by a stint representing Great Britain in A1GP and winning races in Formula 3000. He lives in Indianapolis with his wife Samantha (also from England) and three young "Hoosier" children. He also enjoys racing in triathlons and is rather partial to a good old English cup of tea. But not crumpets.